Offset cores for gas turbine engines

ABSTRACT

A gas turbine engine includes a propulsor with a power turbine, a power turbine shaft extending forward therefrom defining a centerline axis, and a fan driven by the power turbine shaft. The fan is aligned with the centerline axis forward of the power turbine and is operatively connected to be driven by the power turbine through the power turbine shaft. A gas generator operatively connected to the propulsor is included downstream from the fan and forward of the power turbine, wherein the gas generator defines a generator axis offset from the centerline axis. The gas generator is operatively connected to the power turbine to supply combustion products for driving the power turbine.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 62/069,234 filed Oct. 27, 2014, the entire contentsof which are incorporated herein by reference thereto.

BACKGROUND

1. Field

The present disclosure relates to gas turbine engines, and moreparticularly to turbofan engines with offset cores, for example.

2. Description of Related Art

Traditionally, gas turbine engines include a turbine that drives a fanto draw air into the engine as the turbine rotates. The air is typicallysectioned between a bypass duct and a core flow path that leads througha compressor section and a combustor section. Products of thiscombustion pass across turbine rotors which are driven to rotate, and inturn rotate the compressor and fan section. Historically, the fan andcompressor section have been mounted concentrically. Traditionally, oneturbine section drove both the compressor section and the fan at thesame speed. This has been improved upon with a geared turbofan and twoand three spool engines that allow for some uncoupling between turbinespeed and fan and compressor speed. More recently it has been proposedto considerably increase the diameter of the fan section and reduce thecore flow path and engine core, e.g. the compressor section, in aneffort to improve engine efficiency. As the core size decreases relativeto the fan size, it tends to be difficult to design with a large turbineshaft passing down the center of a small compressor section.

Such conventional methods and systems have generally been consideredsatisfactory for their intended purpose. However, there is still a needin the art for improved gas turbine engines.

SUMMARY OF THE DISCLOSURE

A gas turbine engine includes a propulsor with a power turbine, a powerturbine shaft extending forward therefrom defining a centerline axis,and a fan driven by the power turbine shaft. The fan is aligned with thecenterline axis forward of the power turbine and is operativelyconnected to be driven by the power turbine through the power turbineshaft. A gas generator operatively connected to the propulsor isincluded downstream from the fan and forward of the power turbine,wherein the gas generator defines a generator axis offset from thecenterline axis. The gas generator is operatively connected to the powerturbine to supply combustion products for driving the power turbine.

The gas generator can include a compressor section, a combustor section,a turbine section and a turbine shaft defined along the generator axis.The gas turbine engine can include a fan case radially outward of thefan defining a fan inlet along the centerline axis. The gas generatorcan be in fluid communication with the fan inlet through a duct, whereinat least a portion of the duct is angled relative to the centerline axisand the generator axis. The gas turbine engine can include a transitionduct defined between an exhaust outlet of the gas generator and an inletof the power turbine for providing fluid communication therebetween. Thetransition duct can be angled relative to the centerline axis and thegenerator axis.

In accordance with certain embodiments, the gas turbine engine includesan outer core cowl radially inward of the fan case. The outer core cowldefines an axially extending splitter for dividing fluid flow enteringat the fan inlet into a core gas path and a bypass flow path. The coregas path includes a core inlet defined radially between the splitter andan inner core cowl. The core inlet is circumferentially segmented into afirst duct inlet and a second duct inlet. The gas generator is definedin the core gas path downstream of the core inlet in fluid communicationwith the first duct inlet through a first duct.

The second duct inlet can be in fluid isolation from the gas generator.A thermal management system can be defined in a second duct. The thermalmanagement system is in fluid communication with the core gas path andthe second duct inlet through the second duct. The thermal managementsystem can include a heat-exchanger disposed within the second duct aftof the second duct inlet and forward of a second duct outlet. The secondduct can include an exhaust portion with an exhaust outlet separate fromand upstream of an exhaust outlet of a power turbine. The exhaustportion can be angled relative to the centerline axis. The first ductinlet can be defined in a bottom half of the core inlet, or any othersuitable portion of the core inlet. The gas generator can define agenerator axis that is substantially parallel to the centerline axis.The gas turbine engine can include a hub defined forward of the coreinlet. The hub can be configured to direct flow to the first and secondduct inlets. The first and second duct inlets can be configured toapportion incoming fluid flow evenly between the first duct inlet andthe second duct inlet, for example.

In accordance with other embodiments, a gas turbine engine includes anouter core cowl. The outer core cowl is radially inward of the fan case.The first duct is defined between the core inlet and the gas generatorfor fluid communication therebetween. The gas generator can include acompressor section, a combustor section aft of the compressor section,and a turbine section aft of the combustor section. The compressorsection, the combustor section, and the turbine section can be alignedwith the generator axis.

In one embodiment, a gas turbine engine is provided. The gas turbineengine having: a propulsor including a power turbine, a power turbineshaft extending forward therefrom defining a centerline axis, and a fandriven by the power turbine shaft, wherein the fan is aligned with thecenterline axis and is defined forward of the power turbine; and a gasgenerator operatively connected to the propulsor downstream from the fanand forward of the power turbine, wherein the gas generator defines agenerator axis offset from the centerline axis.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, the generator axis maybe substantially parallel to the centerline axis.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, further embodiments mayinclude a fan case radially outward of the fan defining a fan inletalong the centerline axis, wherein the gas generator is in fluidcommunication with the fan inlet through a duct, wherein at least aportion of the duct is angled relative to the centerline axis and thegenerator axis.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, further embodiments mayinclude a transition duct defined between an exhaust outlet of the gasgenerator and an inlet of the power turbine for providing fluidcommunication therebetween, wherein the transition duct is angledrelative to the centerline axis and the generator axis.

In yet another embodiment, a gas turbine engine is provided. The gasturbine engine having: a fan case defining a centerline axis, the fancase including a fan inlet; an outer core cowl radially inward of thefan case defining an axially extending splitter for dividing fluid flowentering at the fan inlet into a core gas path and a bypass flow path,wherein the core gas path includes a core inlet defined radially betweenthe splitter and an inner core cowl; and a gas generator defined in thecore gas path downstream of the core inlet, wherein the core inlet iscircumferentially segmented into a first duct inlet and a second ductinlet, wherein the gas generator is in fluid communication with thefirst duct inlet through a first duct.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, wherein the second ductinlet may be in fluid isolation from the gas generator.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, wherein the gasgenerator defines a generator axis that is substantially parallel to thecenterline axis.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, further embodiments mayinclude a hub defined forward of the core inlet configured to directflow to the first and second duct inlets, wherein the first and secondduct inlets are configured to apportion incoming fluid flow evenlybetween the first duct inlet and the second duct inlet.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, further embodiments mayinclude a transition duct for fluid communication between an exhaustoutlet of the gas generator and an inlet of a power turbine aft of thegas generator.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, wherein the first ductinlet is defined in a bottom half of the core inlet.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, further embodiments mayinclude a thermal management system defined in a second duct, whereinthe thermal management system is in fluid communication with the secondduct inlet and the core gas path through the second duct.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, wherein the second ductincludes an exhaust portion with an exhaust outlet separate from andupstream of an exhaust outlet of a power turbine, wherein the exhaustportion is angled relative to the centerline axis.

In yet another embodiment, a gas turbine engine is provided. The gasturbine engine having: a propulsor including a power turbine defining acenterline axis, and a fan aligned with the centerline axis forward ofthe power turbine operatively connected to be driven by the powerturbine; a fan case defined radially outward of the fan aligned with thecenterline axis, wherein the fan case includes a fan inlet; an outercore cowl radially inward of the fan case defining an axially extendingsplitter for dividing fluid flow entering at the fan inlet into a coregas path and a bypass flow path, wherein the core gas path includes acore inlet defined radially between the splitter and an inner core cowl;a gas generator defined in the core gas path aft of the core inletdownstream from the fan and forward of the power turbine, wherein thegas generator defines a generator axis offset from the centerline axis;a first duct between the core inlet and the gas generator for fluidcommunication therebetween; and a transition duct between an exhaustoutlet of the gas generator and an inlet of the power turbine for fluidcommunication therebetween.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, wherein the core inletis circumferentially segmented into a first duct inlet and a second ductinlet, wherein the second duct inlet is in fluid isolation from the gasgenerator, and wherein the first duct inlet is in fluid communicationwith the gas generator through the first duct.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, further embodiments mayinclude a hub defined forward of the core inlet configured to directflow to the first and second duct inlets, wherein the first and secondduct inlets are configured to apportion incoming fluid flow evenlybetween the first duct inlet and the second duct inlet.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, further embodiments mayinclude a thermal management system defined in a second duct, whereinthe thermal management system is in fluid communication with the coregas path and the second duct inlet through the second duct.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, wherein the gasgenerator includes a compressor section, a combustor section aft of thecompressor section, and a turbine section aft of the combustor sectionwherein the compressor section, the combustor section, and the turbinesection are aligned with the generator axis, wherein the generator axisis substantially parallel to the centerline axis.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, wherein the propulsorincludes a power turbine shaft aligned with the centerline axisextending forward from the power turbine, wherein the power turbine isconfigured to drive the fan through the power turbine shaft.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, wherein the transitionduct is angled relative to the centerline axis and the generator axis.

In addition to one or more of the features described above, or as analternative to any of the foregoing embodiments, wherein at least aportion of the first duct is angled relative to the centerline axis andthe generator axis.

These and other features of the systems and methods of the subjectdisclosure will become more readily apparent to those skilled in the artfrom the following detailed description of the preferred embodimentstaken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those skilled in the art to which the subject disclosureappertains will readily understand how to make and use the devices andmethods of the subject disclosure without undue experimentation,preferred embodiments thereof will be described in detail herein belowwith reference to certain figures, wherein:

FIG. 1 is a schematic cross-sectional side elevation view of a gasturbine engine constructed in accordance with embodiments of thedisclosure, showing the gas turbine engine with an offset gas generator;and

FIG. 2 is a schematic front perspective view of a portion of the gasturbine engine of FIG. 1, showing the core inlet segmented into firstand second duct inlets.

DETAILED DESCRIPTION OF THE DISCLOSURE

Reference will now be made to the drawings wherein like referencenumerals identify similar structural features or aspects of the subjectdisclosure. For purposes of explanation and illustration, and notlimitation, an exemplary embodiment of a gas turbine engine inaccordance with the disclosure is shown in FIG. 1 and is designatedgenerally by reference character 100. Other embodiments of gas turbineengines in accordance with the disclosure, or aspects thereof, areprovided in FIG. 2, as will be described.

As shown in FIG. 1, a gas turbine engine 100 includes a propulsor 101having a power turbine 102 and a turbine shaft 104. Power turbine shaft104 extends forward from power turbine 102 defining a centerline axis A.Propulsor 101 also includes a fan 106 aligned with centerline axis Aforward of power turbine 102 and is operatively connected to be drivenby power turbine 102 through power turbine shaft 104. A fan case 110 isdefined radially outward of fan 106 along centerline axis A and includesa fan inlet 114. A nacelle 113 is defined radially outward of fan case110. An outer core cowl 112 is radially inward of fan case 110 anddefines an axially extending splitter 116 for dividing fluid flowentering at fan inlet 114 into a core gas path 118 and a bypass flowpath 120. Core gas path 118 includes a core inlet 122 defined radiallybetween splitter 116 and an inner core cowl 124.

With continued reference to FIG. 1, a gas generator 108 is defineddownstream from fan 106 in core gas path 118 aft of core inlet 122. Gasgenerator 108 defines a generator axis B. Generator axis B is offsetfrom centerline axis A. It is contemplated that generator axis B can besubstantially parallel to centerline axis A. Gas generator 108 includesa compressor section 130 aligned with generator axis B. Compressorsection 130 is operatively connected to power turbine 102 by way of acombustor section 132 and a turbine section 135 to supply combustionproducts for driving power turbine 102. Gas generator 108 includes aturbine shaft 133 defined along generator axis B. Those skilled in theart will readily appreciate that this allows turbine shaft 104 to beoptimally sized for both torque and rotor-dynamics.

Gas turbine engine 100 includes a transition duct 140 defined between anexhaust outlet 142 of gas generator 108, e.g. an outlet of turbinesection 135, and an inlet 144 of turbine 102 for providing fluidcommunication therebetween. Transition duct 140 is angled relative tocenterline axis A and generator axis B. Those skilled in the art willreadily appreciate that off-set gas generator 108 includes compressorsection 130, combustor section 132 and turbine section 135, and isoperatively connected to the same power turbine 102 that is driving fan106. The exhaust from gas generator 108 is ducted to power turbine 102through transition duct 140, and power turbine 102 drives fan 106,either through a fan drive gear system (FDGS) or a direct drive. Theexhaust flow from gas generator 108 is evenly distributed between thetop and bottom halves of transition duct 140 so that it uniformly feedspower turbine 102.

As shown in FIG. 2, core inlet 122 is circumferentially segmented into afirst duct inlet 124 and a second duct inlet 126. Gas generator 108,shown in FIG. 1, is in fluid communication with core inlet 122 and firstduct inlet 124 through a first duct 128. First duct inlet 124 is definedin a bottom half 160 of core inlet 122. At least a portion of first duct128 is angled relative to centerline axis A and generator axis B, shownin FIG. 1. Gas turbine engine 100 includes a hub 156 defined forward ofcore inlet 122. Hub 156 can be configured to direct flow to first andsecond duct inlets, 124 and 126, respectively. First and second ductinlets, 124 and 126, respectively, are configured to apportion incomingfluid flow evenly between first duct inlet 124 and second duct inlet126. While the first and second duct inlets, 124 and 126, respectively,are shown herein as being divided evenly, those skilled in the art willreadily appreciate that the proportions of first duct inlet 124 andsecond duct inlet 126 can vary as needed for a given application.

Now with reference to FIGS. 1 and 2, second duct inlet 126 is in fluidisolation from gas generator 108. It is contemplated that by segmentingcore inlet 122, the second portion of air not needed for gas generator108 can be diverted into second duct inlet 126 which can be used for avariety of suitable purposes, for example, a thermal management system146. Thermal management system 146 includes a heat-exchanger 150 and isdefined in a second duct 148 between second duct inlet 126 and a secondduct outlet 152, e.g. an exhaust outlet. Thermal management system 146is in fluid communication with core gas path 118 and second duct inlet126 through second duct 148. By having second duct inlet 126 and secondduct 148, air flow distortions around hub 156 tend to be mitigated ascompared to if the air flow was taken into first duct inlet 124 alone.For example, if air flow was taken into first duct inlet 124 and therewas no inlet on the top half of hub 156, e.g. second duct inlet 126,there would be significant fluid distortion, e.g. variation in flow rateand/or pressure, around the circumference of hub 156 and/or fan 106,which tends to factor into the propulsor efficiency potentially causingnegative performance results in the engine. By drawing an equal amountair flow from the top of hub 156, the distortion downstream of the fanis mitigated, reducing performance losses.

With continued reference to FIGS. 1 and 2, second duct 148 includes anexhaust portion 154 with exhaust outlet 152 separate from and upstreamof an exhaust outlet 158 of power turbine 102. Exhaust portion 154 isangled relative to centerline axis A. Exhaust outlet 152 is in fluidcommunication with bypass duct 120 for discharging the air flow thereto.Those skilled in the art will readily appreciate that while second duct148 is described herein as having thermal management system 146 disposedtherein, there are a variety of suitable auxiliary components andsystems that can be disposed in second duct 148. For example, the airflow can be utilized as part of an anti-ice system, an environmentalcontrol system, and/or any other suitable auxiliary components andsystems. It is contemplated that the above described components andsystems can be disposed directly in second duct 148, and/or operativelyconnected thereto.

The systems, devices and methods of the present disclosure, as describedabove and shown in the drawings, provide for gas turbine engines withsuperior properties including increased engine efficiency due to reducedlosses, increased thermal management efficiency, increased ease ofdesign, assembly and maintenance, and reduction of overall weight. Whilethe apparatus and methods of the subject disclosure have been shown anddescribed with reference to preferred embodiments, those skilled in theart will readily appreciate that changes and/or modifications may bemade thereto without departing from the scope of the subject disclosure.

What is claimed is:
 1. A gas turbine engine comprising: a propulsorincluding a power turbine, a power turbine shaft extending forwardtherefrom defining a centerline axis (A), and a fan driven by the powerturbine shaft, wherein the fan is aligned with the centerline axis andis defined forward of the power turbine; a gas generator operativelyconnected to the propulsor, wherein the gas generator comprises acompressor and a combustor and the gas generator is located between thefan and the power turbine, the gas generator defining generator axis (B)offset from the centerline axis; a fan case radially outward of the fandefining a fan inlet along the centerline axis (A), wherein the fanextends radially and radially traverses the gas generator in entiretyand wherein the gas generator is in fluid communication with the faninlet through a duct, wherein at least a portion of the duct is angledrelative to the centerline axis and the generator axis (B); a nacelleradially outward of the fan case, wherein the nacelle encloses the fancase and the gas generator; and a transition duct defined between anexhaust outlet of the gas generator and an inlet of the power turbinefor providing fluid communication therebetween, wherein the transitionduct is angled relative to the centerline axis (A) and the generatoraxis (B).
 2. A gas turbine engine as recited in claim 1, wherein thegenerator axis (B) is substantially parallel to the centerline axis (A).3. A gas turbine engine comprising: a fan case defining a centerlineaxis (A), the fan case including a fan inlet; a fan located within thefan case, the fan being driven by a power turbine operably coupled tothe fan by a power turbine shaft, wherein the fan, the power turbine andthe power turbine shaft are aligned with the centerline axis; a gasgenerator comprising a compressor and a combustor, wherein the gasgenerator is located between the fan and the power turbine; an outercore cowl radially inward of the fan case defining an axially extendingsplitter for dividing fluid flow entering at the fan inlet into a coregas path and a bypass flow path, wherein the core gas path includes acore inlet defined radially between the splitter and an inner core cowl;a nacelle radially outward of the fan case, wherein the nacelle enclosesthe fan case and the gas generator, and wherein the fan extends radiallyand radially traverses the gas generator in entirety; and the gasgenerator located entirely within the core gas path downstream of thecore inlet, the gas generator defining a generator axis (B) that isoffset from the centerline axis, wherein the entire gas generator islocated radially inward from the outer core cowl.
 4. The gas turbineengine as in claim 3, further comprising a transition duct definedbetween an exhaust outlet of the gas generator and an inlet of the powerturbine for providing fluid communication therebetween.
 5. The gasturbine engine as in claim 4, wherein the transition duct is angledrelative to the centerline axis (A) and the generator axis (B).